Announcement

Collapse
No announcement yet.

Loss of engine power; Mercruiser 5.0l MPI/Bravo 3-gctid815795

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

    Loss of engine power; Mercruiser 5.0l MPI/Bravo 3-gctid815795

    Hi all,

    You folks have helped me out before so I'm hoping this learned group can do so again.

    We took our Maxum 2600SE out on the SF Bay for two trips in May/June this year. The engine seemed to perform fine, with the exception of slightly elevated fuel burn (17 gph vs 13.5 gph on plane). This is a chronic problem on our boat, and I have fixed this in the past by replacing the fuel filter and cup and the lower fuel pressure regulator. A new fuel filter and cup did not correct the problem. I removed the FPR and saw that the screen was covered in black crud so I replaced it.

    We launched again on July 1. Everything seemed normal at idle and displacement speeds (up to 8 knots). When I tried to go on plane, I could not get the boat RPM above 3000. I was not able to get on plane or go faster than ~13 knots. I ran the boat for about an hour trying to see if the engine performance changed. Gradually our speed dropped to 8 knots and the engine power and RPM seemed to fluctuate. I then brought the boat back to the launch ramp.

    Today I checked several things. The FPR was removed to see if the o-rings had been compromised when I installed it, but they were fine. I checked the engine oil for signs of water but it looks fine. I checked the upper FPR and it looked fine. I checked the distributor cap and rotor and they seem fine. The air filter looked a little dirty but doesn't seem to be bad enough to cause this problem.

    Any obvious things that I haven't checked? Thanks in advance for any wisdom you can offer!

    Tom
    2006 Maxum 2600SE with Merc 5.0L MPI/Bravo III

    #2
    Cool fuel Gen lll should be on your 2006 MPI Engine.

    Fuel pressure running high due to its clogged fuel system most likely.

    When you replaced the paper filter, did you also replace the white disc filter also?

    That's the important one!

    Major problem with paint peeling , clogging up everything inside the module.
    Joon, Kathy, Jaden & Tristan
    93 3058
    92 2855
    91 Fourwinns 205
    Longbranch WA
    Life is Good

    Comment


      #3
      Thanks for the reply. Yes, I do have the Cool Fuel Gen 3 and am aware of the paint peeling problem (which by the way, Mercury Marine refuses to acknowledge). This is why I've had to regularly replace the filter, disk and the FPR at various times.

      This new problem could be due to clogging in other areas I suppose. Maybe the injectors? The upper FPR (on the rail) looks clean.

      I'm wondering if the fuel pump is giving out.

      I also wonder if I should break down and replace the Cool Fuel module. It's expensive ($1000) and I have no idea if Mercury has corrected the paint overspray problem at the factory.
      2006 Maxum 2600SE with Merc 5.0L MPI/Bravo III

      Comment


        #4
        My pleasure Ice!

        First check the fuel pressure at the fuel rail.

        Yes something is getting clogged up most likely. The module isn't cheap about a BOAT bucks.

        I would pull the module, disassemble everything, check the inlet screen filter on BOTH high & low fuel pumps.
        Joon, Kathy, Jaden & Tristan
        93 3058
        92 2855
        91 Fourwinns 205
        Longbranch WA
        Life is Good

        Comment


          #5
          OK so I've taken this boat to a mechanic and he's done some diagnostics, but there is still no resolution. There were no fault codes and the engine telemetry looks normal (including under load). He's leaning towards a cylinder leak problem. He did a compression test and all cylinders were OK but 2 and 4, which tested at 130 psi, but after he sprayed in some oil they tested normal. He wants to do a leak down test, but I'm not sure he's on the right track since the engine SOUNDS fine at low speeds and even under heavy load, it just can't deliver enough power. Also the engine has been running fine up until two weeks before the July 1 launch. It's hard to believe a cylinder problem would manifest suddenly.

          Another mechanic told me that with cars, typically two things can cause the engine to not get full power: a fuel delivery problem, and a blockage of the exhaust system.

          The fuel pressure seems to be normal, and as I mentioned I replaced a component that was clogged. But I suppose there could be another problem that isn't detected by the engine computer.

          I don't really understand how exhaust gasses leave the engine. I believe they leave via the stern drive, but I don't know how they get there. Are they routed to the exhaust manifold that is used for raw water exhaust? Or is there a separate set of manifolds/pipes? Is there something that could get blocked and should be checked?
          2006 Maxum 2600SE with Merc 5.0L MPI/Bravo III

          Comment


            #6
            "iceman11" post=822353 wrote:
            OK so I've taken this boat to a mechanic and he's done some diagnostics, but there is still no resolution. There were no fault codes and the engine telemetry looks normal (including under load). He's leaning towards a cylinder leak problem. He did a compression test and all cylinders were OK but 2 and 4, which tested at 130 psi, but after he sprayed in some oil they tested normal. He wants to do a leak down test, but I'm not sure he's on the right track since the engine SOUNDS fine at low speeds and even under heavy load, it just can't deliver enough power. Also the engine has been running fine up until two weeks before the July 1 launch. It's hard to believe a cylinder problem would manifest suddenly.

            Another mechanic told me that with cars, typically two things can cause the engine to not get full power: a fuel delivery problem, and a blockage of the exhaust system.

            The fuel pressure seems to be normal, and as I mentioned I replaced a component that was clogged. But I suppose there could be another problem that isn't detected by the engine computer.

            I don't really understand how exhaust gasses leave the engine. I believe they leave via the stern drive, but I don't know how they get there. Are they routed to the exhaust manifold that is used for raw water exhaust? Or is there a separate set of manifolds/pipes? Is there something that could get blocked and should be checked?
            I just posted a response to the identical post on the Maxum owners club for you.
            1997 Maxum 2400 SCR 5.7LX Bravo II

            Mike

            Comment


              #7
              I would be looking into the exhaust.... there are flappers in there just below the elbows that can fail and plug the exhaust tube.... one side plugs and 3000rpm is about all you get out of it when in gear in the water...

              its a cheap and easy fix if thats what the problem is, and reasonably simple to check, it only requires pulling the elbows off and looking down the tubes.

              one side or theother may be stuck closed or if it broke a pivot hole, it will be jammed in there, and if it broke both pivot holes, it will be down farther in the exhaust tube, in which case it may require pulling the outdrive to extract it.


              NU LIBERTE'
              Salem, OR

              1989 Bayliner 2556 Convertible
              5.7 OMC Cobra - 15.5x11 prop
              N2K equipped throughout..
              2014 Ram 3500 crew cab, 6.7 Cummins
              2007 M-3705 SLC weekend warrior, 5th wheel
              '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
              Heavy Equipment Repair and Specialty Welding

              Comment


                #8
                "Centerline2" post=822456 wrote:
                I would be looking into the exhaust.... there are flappers in there just below the elbows that can fail and plug the exhaust tube.... one side plugs and 3000rpm is about all you get out of it when in gear in the water...

                its a cheap and easy fix if thats what the problem is, and reasonably simple to check, it only requires pulling the elbows off and looking down the tubes.

                one side or theother may be stuck closed or if it broke a pivot hole, it will be jammed in there, and if it broke both pivot holes, it will be down farther in the exhaust tube, in which case it may require pulling the outdrive to extract it.
                +1
                Joon, Kathy, Jaden & Tristan
                93 3058
                92 2855
                91 Fourwinns 205
                Longbranch WA
                Life is Good

                Comment


                  #9
                  Centerline: If the exhaust was blocked, shouldn't the boat have overheated as well? The raw cooling water exits the same way, right? The engine temp was normal while I was on the water.
                  2006 Maxum 2600SE with Merc 5.0L MPI/Bravo III

                  Comment


                    #10
                    "iceman11" post=822494 wrote:
                    Centerline: If the exhaust was blocked, shouldn't the boat have overheated as well? The raw cooling water exits the same way, right? The engine temp was normal while I was on the water.
                    Thinking about this the exhaust is not going to be totally blocked if the flappers broke off and are laying in the bottom of the y-pipe so while the exhaust is restricted gases and water can still pass however I would still expect a rise in operating temp.
                    1997 Maxum 2400 SCR 5.7LX Bravo II

                    Mike

                    Comment


                      #11
                      First post Ice wrote " black crud "

                      Hoses may be compromised from this new fuel.

                      What happens and i've seen this more and more ...

                      Spend a week chasing a lack of power condition.

                      Went thru the list i copied and pasted below, what did it turn out to be ?

                      Inner lining of the fuel hose peels away, leave " black crud " in a filter, clean it out or replace the filter, and think nothing of it.

                      Turns out the inner lining can and will block the fuel hose.

                      Owner of the boats don't even mention the " crud " i have to keep prodding them what was done to the boat, was it acting up before, then they say or mention something about " crud " in a filter.

                      Take a peek at the list :

                      This is a generic list you don't have a carb: for example.

                      1. Fuel condition. Type and Octane possibly old fuel.

                      2. Propeller pitch or diameter, damaged blades. Wrong prop ...

                      3. Restricted fuel pickup tube or anti siphon valve Fuel System Test

                      4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse

                      5. Marine growth on hull and outdrive.

                      6. Wrong gear ratio in outdrive.

                      7. Restricted carburetor air intake (clogged flame arrestor).

                      8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive.

                      9. Poor cylinder compression Compression Test.

                      10. Carburetor defective, or wrong type.

                      11. Fuel pump pressure and vacuum

                      12. Boat overloaded, improperly loaded, or improperly trimmed.

                      13. Engine Overheating.

                      14. Engine timing and ignition system operation. Plugs, wires, etc.

                      14A- Check the dist. shaft some have a c-clip some don't, wiggle the shaft.

                      15. Remote control cables and linkage for proper travel to open throttle plates fully.

                      16-Valves need adjusting.

                      17-Hidden water in the hull.

                      18- Fuel hose degradation.

                      Above copied and pasted from another website: #16 and #17 added by myself. Now i'm adding fuel hose degradation.

                      When I am asked to check wot on friends boats, I make sure the tank is half full, engine freshly tuned up.

                      Hull must be clean, doesn't help when the guy say's oh yea 3-5 weeks ago, nope freshly cleaned hull.

                      You have water tanks, 8.34 pounds per gallon of water. You do the math. That's fresh water, saltwater more.
                      Be good, be happy, for tomorrow is promised to no man !

                      1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !

                      '86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !

                      Manalapan N.J

                      Comment


                        #12
                        "Chief Alen" post=822550 wrote:


                        Spend a week chasing a lack of power condition.

                        Went thru the list i copied and pasted below, what did it turn out to be ?

                        Inner lining of the fuel hose peels away, leave " black crud " in a filter, clean it out or replace the filter, and think nothing of it.

                        Turns out the inner lining can and will block the fuel hose.
                        Well I definitely saw black crud on the lower FPR (the one mounted on the Cool Fuel module). The boat was running fine with this condition, except for high fuel burn rate. The problem started after I replaced the FPR (and had already previously replaced the fuel filter and disk).

                        It sounds like you're saying a fuel hose itself could be internally blocked? How would I isolate the hose causing this problem? Would the fuel pressure on the rail tell me anything? Or would I just have to remove the hoses and inspect them visually?

                        Thanks for the list. A lot of those items don't apply (boat sits on trailer for example so bottom is clean) but there are definitely things that need to be checked.
                        2006 Maxum 2600SE with Merc 5.0L MPI/Bravo III

                        Comment


                          #13
                          Don't recall but you have already checked this out. There have been issues with the cool fuel getting internally blockage from being internally painted. Fuel pressure at the rail would be low.
                          1997 Maxum 2400 SCR 5.7LX Bravo II

                          Mike

                          Comment


                            #14
                            We are experiencing the same problem. Did you find the cause?

                            Comment


                              #15
                              Ice:

                              i included a pic and link below.

                              Damn expensive for a piece of hose, but in the scheme of things cost wise a good investment.

                              Is the hose your problem don't know,

                              i also heard about the cool fuel paint messing chit up, paint melts in a NY second when fuel touch's it.

                              I refitted my last 2 boats when i got them, with new hose ... the fill hose is the most expensive,

                              Could it be water in your fuel, maybe phase separation ?

                              May sound crazy to you i had that problem.

                              Starting about 10 years maybe longer, before starting the boat for the first time after layup, i crank the bow up ... my boats are trailer queens, stick a hose down in the tank dead center, and pump the gunk and junk off the bottom of the tank into a snapple glass bottle, always glass jar, never plastic, eats right thru plastic.

                              When the fuel runs clear i shut off the pump.

                              Then i follow the hose to the next stop clean as i go the turns are the worst, and i found my channels in the bracket that hold the element clogged. I learned my lesson.

                              From tank to carb or in your case efi you need a clean system.

                              When you are 1000% sure of a clean system, run the boat, if your still have the problem then it's time to go after fuel injectors etc.

                              http://www.ebay.com/itm/SHIELDS-368-...-/232408830702


                              Be good, be happy, for tomorrow is promised to no man !

                              1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !

                              '86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !

                              Manalapan N.J

                              Comment

                              Working...
                              X